A nucleotide resolution map of Top2-linked DNA breaks in the yeast and human genome

Abstract

DNA topoisomerases are required to resolve DNA topological stress. Despite this essential role, abortive topoisomerase activity generates aberrant protein-linked DNA breaks, jeopardising genome stability. Here, to understand the genomic distribution and mechanisms underpinning topoisomerase-induced DNA breaks, we map Top2 DNA cleavage with strand-specific nucleotide resolution across the S. cerevisiae and human genomes—and use the meiotic Spo11 protein to validate the broad applicability of this method to explore the role of diverse topoisomerase family members. Our data characterises Mre11-dependent repair in yeast and defines two strikingly different fractions of Top2 activity in humans: tightly localised CTCF-proximal, and broadly distributed transcription-proximal, the latter correlated with gene length and expression. Moreover, single nucleotide accuracy reveals the influence primary DNA sequence has upon Top2 cleavage—distinguishing sites likely to form canonical DNA double-strand breaks (DSBs) from those predisposed to form strand-biased DNA single-strand breaks (SSBs) induced by etoposide (VP16) in vivo.

Abstract

Topoisomerase 2 (Top2) is known to resolve DNA topological stress through double strand breaks (DSBs), yet Top2 inhibition has been reported to result in a significant amount of single-strand breaks (SSBs). Here the authors develop CC-seq—a method that allows direct mapping of both Top2-linked SSBs and DSBs—and reveal a significant impact of primary DNA sequence on Top2 directed cleavage.